In many industrial environments it is desirable to detect and sense physical loads. For example, in a parts handling system using a robot, it is necessary to detect the presence of an object or the collision between the robot and the surrounding environment. Various sensors, such as strain gauges, load cells, and photocell interrupter switches, have been only marginally successful in this regard due to problems such as bias offsets and the limitation that they cannot be compressed without destruction.
In an improved but not entirely satisfactory technique, piezoelectric sensors have been employed for sensing forces wherein a piezoelectric material generates a voltage potential in response to a compressive force. Typically, the piezoelectric sensor is mechanically biased by compressing it between two surfaces so that both compressive and expansive forces may be measured. A major limitation of the piezoelectric sensor is that it is prone to large variances in bias and does not adapt well to dynamic load changes. Moreover, the rudimentary signal conditioning circuitry previously used for piezoelectric sensors tends to drift and requires constant adjustment for accurate measurement.
Accordingly, it can be seen that there is a need for a load sensing system and method which is rugged, accurate, and is easily adaptable to robotic applications.